Three major types of interferons have been identified in humans: alpha-, beta-, and gamma-interferons. These are produced by a variety of cells upon exposure to viruses, mitogens, polynucleotides etc. They possess anti-viral, anti-proliferative and immunomodulatory properties. IFN-β is used as an effective treatment for multiple sclerosis [Corboy J R. et al., Current Treatment Options in Neurology, 5, 35-54 (2003)], hepatitis B and hepatitis C.
Betaseron, an analogue of human IFN-β where serine was genetically engineered to substitute for cysteine at position 17, is known as IFN-β 1b (U.S. Pat. No. 4,588,585). The molecule is a small polypeptide of 165 amino acids with a single disulphide bond, and is produced as a non-glycosylated protein. The glycosylated variant of IFN-β, known as IFN-β 1a, has a carbohydrate chain at position 80 and is expressed in Chinese Hamster Ovary cells [Conradt et al., J. Biol. Chem., 262, 14600-5 (1987); Kagawa et al., J. Biol. Chem., 263, 17508-15 (1988); Oh et. al., Biotechnol. Prog., 21, 1154-64 (2005); U.S. Pat. No. 5,795,779 (McCormik et al); U.S. Pat. No. 5,554,513 (Revel et al)].
IFN-β was initially produced by inducing the leukocytes by treating them with viruses. But the therapeutic use of interferon-β produced in this manner is questionable because of the high chances of the presence of various contaminants (e.g. viruses) in such preparations. Recombinant technology has made it possible to produce IFN-β, which is free from viral contamination. Native IFN-β is a glycoprotein, and its production has been reported in mammalian, insect and yeast cells, as described in Mantei et al., Nature 297: 128 (1982); Ohno et al., Nucl Acid. Res. 10: 967 (1982); and Smith et al., Mol. Cell. Biol. 3: 2156 (1983), respectively.
U.S. Pat. No. 5,795,779 (McCormick et al.) discloses high level production of IFN-β from recombinant CHO cells. U.S. Pat. No. 5,554,513 (Revel et al.) discloses two subtypes of IFN-β and describes methods to produce it in CHO cells. But a!! commercial animal cell culture processes are associated with technical difficulties like, longer process time, requirement for maintaining stringent culturing conditions, high cost of culture media etc.
Also, the glycosylation was shown to play no role in the biological activity of the protein [Taniguchi, et al., Gene 10, 11-15 (1980); E. Knight Jr., Proc. Natl Acad. Sci., 73, 520 (1976); E. Knight Jr. and D. Fahey, J. Interferon Res. 2(3), 421 (1982)] thereby underscoring the advantage of carrying out the production in the commonly used host, E. coli. Various recombinant proteins have been produced in E. coli by this technology [Saraswat et al. FEMS Microbiology Lett., 179, 367-73 (1999); Holowachuk & Ruhoff, Protein Expr. Purif. 6, 588-96 (1995); Kim et. al, Biotechnol. & Bioeng., 69, (2000); Kim et al., Bioprocess and Biosystems Engineering, 24 (2001); Saraswat et. al. Biotechnol. Lett., 22, 261-5 (2000); Lee et. al., FEMS Microbiology Lett., 195, 127-132 (2001); Saraswat et. al. Biochemistry, 41, 15566-77 (2002); Wang et al., Chin. J. Biotechnol. 11, 45-81 (1995)].
IFN-β has been cloned and expressed in E. coli (Taniguchi, et al., Gene 10, 11-15 (1980).
EP 0048970 (Goeddel et al.) describes microbial production of mature human fibroblast interferon.
Like for any therapeutic protein, it is desirable to obtain high levels of interferon-β for commercial purposes. EP 0036776 (Kield et al.) discloses novel vectors based on tryptophan promoter-operator system for the efficient production of heterologous protein in bacteria. U.S. Pat. No. 4,686,191 (Itoh et al.) discloses methods to obtain efficient expression of interferon-β in E. coli, by using improved vectors with trp promoter, to increase the efficiency of protein synthesis. U.S. Pat. No. 4,499,188 (Konrad et al.) claims to solve the problem of monitoring repressor levels during culturing, when trp promoter is used for interferon-β production. Mizukami et al. in U.S. Pat. No. 4,746,608 suggest the method of culturing the recombinant microorganism at a temperature 10 to 25° C. lower than the optimum growth temperature, for obtaining a high yield of interferon-β. Ben-Bassat et al. in U.S. Pat. No. 4,656,132 claim to solve the problem of lower yields of interferon-β by addition of an effective amount of a water-soluble alkanol of 1 to 4 carbon atoms and/or a mixture of amino acids that supports bacterial growth during the late phase of the cultivation. Cousens et al. in U.S. Pat. No. 5,866,362 have suggested the production of interferon-β as protein aggregates by growing the host cells in a medium comprising an effective amount of Cu++ so that they form inclusion bodies in the host cell from which the protein is isolated and purified. But none of the processes could achieve satisfactory levels of interferon-β. Because of the hydrophobic nature of interferon-β, the synthesized protein interferes with cell growth and thus the production of interferon-β is not achieved at significantly high levels.
Dorin et al. in U.S. Pat. No. 5,814,485 disclose certain conditions that increase the expression of hydrophobic polypeptide like interferon-β in transformed host cells. The critical conditions for the invention (U.S. Pat. No. 5,814,485) arc Potassium ion concentration no greater than 120 mM and/or Sodium ion concentration no greater than 40 mM and/or p11 between 4.8 and 6.8 during the induction of protein production.
The present invention discloses similar to higher level of production of interferon-β as that disclosed in U.S. Pat. No. 5,814,485 by inducing the protein production at conditions, which are not dependent on maintaining low levels of Potassium and Sodium ion concentrations in the production media. This is achieved by careful selection of the nitrogen source and other nutrients/additives before or during the production phase.